A variety of mechanical configurations that retain a shaft in such a manner that the shaft is movable in the axis direction are known. Examples of the configurations include, e.g., a shaft retainer of a linear motion actuator. In a situation in which a shaft retainer of actuators is used under a relatively high temperature environment, heat that is transferred through the shaft retainer from the outside to the inside of the actuator or other devices may cause troubles in the operation of a driving part such as a motor or the like, or lead to loss of function of a component composed of a material with low heat-resistance capability, for example. Accordingly, various efforts have been made to prevent heat transfer from the outside to the inside of devices, including an actuator.
For example, Patent Document 1 discloses a technique for protecting a rubber boot, which seals a clearance between a shaft and a boss to prevent ingress of water, dust, and so on into the inside of the actuator, by using a heat shield cover having a bottomed cylindrical shape. With this cover, heat transfer to the inside of the actuator is mitigated to some extent.